Bulletin of the American Physical Society
89th Annual Meeting of the Southeastern Section of the APS
Volume 67, Number 18
Thursday–Saturday, November 3–5, 2022; University of Mississippi, University, MS
Session C02: Cosmology and Tests of General Relativity |
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Chair: Aklant Bhomick, University of Florida Room: University of Mississippi Ballroom B |
Thursday, November 3, 2022 2:00PM - 2:30PM |
C02.00001: Preparing for Supernova Cosmology With the Nancy Grace Roman Space Telescope Invited Speaker: Benjamin Rose The Nancy Grace Roman Space Telescope is a wide-field infrared telescope that will launch before mid-2027. With 100 times the field of view of the Hubble Space Telescope, the Roman Space Telescope is designed for cosmological surveys. I will present an overview of the Roman Space Telescope's capabilities and the three main legacy surveys. Including its vast archive and guest-observer capabilities, Roman is a telescope for the entire astrophysics community. One target experiment is a revolutionary Type Ia supernovae survey. From the High Latitude Time Domain survey, Roman will observe ~12,000 SNe Ia with most of them being above a redshift of one. This large data set is designed to be used to make the most precise measurement of the time dependence of Dark Energy. In addition, Roman should shed light on the solution to the current Hubble constant tension. To make this measurement, Roman will need to control both hardware and astrophysical systematics. In this talk, I will explain the current efforts to ensure Roman's calibration, as well as improved analysis models and methods. This work allows Roman to make this extremely precise measurement of Dark Energy, improve our understanding of SN Ia, and shed light on the Hubble constant tension. |
Thursday, November 3, 2022 2:30PM - 3:00PM |
C02.00002: Cosmography with bright and aphotic sirens with Love Invited Speaker: Anuradha Gupta Precision cosmology is crucial to understand the different energy components in the Universe and their evolution through cosmic time. Gravitational wave sources are standard sirens that can accurately map out distances in the Universe. Together with the source redshift information, we can then probe the expansion history of the Universe. We explore the capabilities of various gravitational-wave detector networks to constrain different cosmological models while employing separate waveform models for inspiral and post-merger parts of the gravitational-wave signal from equal mass binary neutron stars. We consider two different avenues to measure the redshift of a gravitational-wave source: first, we examine an electromagnetic measurement of the redshift via either a kilonova or a gamma-ray burst detection following a binary neutron star merger (the electromagnetic counterpart method); second, we estimate the redshift from the gravitational-wave signal itself from the adiabatic tides between the component stars characterized by the tidal Love number, to provide a second mass-scale and break the mass-redshift degeneracy (the counterpart-less method). We find that the electromagnetic counterpart method is better suited to measure the Hubble constant while the counterpart-less method places more stringent bounds on other cosmological parameters. In the era of next-generation gravitational-wave detector networks, both methods achieve sub-percent measurement of the Hubble constant $H_0$ after one year of observations. The dark matter energy density parameter $Omega_{ m M}$ in the $Lambda$CDM model can be measured at percent-level precision using the counterpart method, whereas the counterpart-less method achieves sub-percent precision. We, however, do not find the postmerger signal to contribute significantly to these precision measurements. |
Thursday, November 3, 2022 3:00PM - 3:12PM |
C02.00003: Towards a more robust algorithm for computing the Kerr quasinormal mode frequencies Sashwat Tanay Leaver's method has been the standard for computing the quasinormal mode (QNM) frequencies for a Kerr black hole (BH) for a few decades. We start with a spectral variant of Leaver's method introduced by Cook and Zalutskiy (arXiv: 1410.7698) and propose improvements in the form of computing the necessary derivatives analytically, rather than by numerical finite differencing. We also incorporate this derivative information into qnm, a Python package, which finds the QNM frequencies via the spectral variant of Leaver's method. We confine ourselves to first derivatives only. |
Thursday, November 3, 2022 3:12PM - 3:24PM |
C02.00004: When can we ignore eccentricity when testing general relativity with gravitational waves? Purnima Narayan, Nathan Johnson-McDaniel, Anuradha Gupta Detections of gravitational waves (GW) emitted from binary black hole (BBH) coalescences allow us to probe the strong-field dynamics of general relativity (GR). One can compare the observed GW signals with theoretical waveform models to constrain possible deviations from GR. Any physics that is not included in these waveform models might show up as apparent GR deviations. The waveform models used in current tests of GR describe binaries on quasicircular orbits, since most of the binaries detected by ground-based gravitational wave detectors are expected to have negligible eccentricities. Thus, a signal from an eccentric binary in GR is likely to show up as a deviation from GR in the current implementation of these tests. We study the response of four standard tests of GR to numerically simulated eccentric BBH signals in the LIGO-Virgo network. Specifically, we consider a test for the consistency between the low- and high-frequency parts of the signal; two tests that introduce parameterized modifications to the phase of the signal (e.g., in the post-Newtonian coefficients); and a test for dispersive propagation effects. We find that signals having larger eccentricities (~0.1) when entering the detector's sensitive band lead to very significant false GR deviations in most tests for the high-SNR cases we consider, while signals having smaller eccentricities (~0.05) still lead to significant deviations in some tests. Thus, it will be necessary to exclude the possibility of an eccentric binary in order to make any claim about detecting a deviation from GR. |
Thursday, November 3, 2022 3:24PM - 3:36PM |
C02.00005: I-Love-Q in Einstein-aether Theory Kai Vylet, Siddarth Ajith, Kent Yagi, Nicolas Yunes Einstein-aether theory is a modified theory of gravity which breaks gravitational Lorentz invariance by introducing a vector field called the aether. This vector field is unit, timelike and gives a preferred time direction at each point in space. Einstein-aether theory has four free parameters which characterize deviations from General Relativity and which must be determined, or constrained, by experimental observations. Although three of the four parameters have been constrained by various empirical observations and stability requirements, one, called cω, remains elusively unconstrained. The goal of this project is to see if it is feasible to use neutron star observations to constrain cω. Specifically, we aim to see if a constraint can be derived from the I-Love-Q universal relations, which are relations between the neutron star moment of inertia (I), tidal Love number (Love) and quadrupole moment (Q). These relations are useful for utilizing neutron star observables because they are insensitive to uncertainties in the neutron star equation-of-state. To understand if the theory can be constrained through such relations, we derive the I-Love-Q quantities in Einstein-aether theory and see if any of them depend on cω. |
Thursday, November 3, 2022 3:36PM - 3:48PM |
C02.00006: Thermodynamics to infer the astrophysics of binary black hole mergers Patrick T Hu, Karan Jani, Kelly Holley-Bockelmann, Gregorio Carullo We have created a novel technique to infer the properties and astrophysical implications of binary black holes by measuring the entropy transfer in their evolution. By applying it to GW190521 – the heaviest binary black hole merger observed so far by LIGO/Virgo - we gain new insights into its origins. |
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